Prevention of HIV-1 infection requires a more detailed knowledge of HIV-1 transmission than is currently available. Tremendous progress on understanding the pathogenesis of HIV-1 has been made through animal experiments and by clinical translational research. But the most critical information can only be obtained through intensive study of subjects with newly acquired (acute) HIV-1, and if at all possible, the study of "transmission pairs". Unfortunately, it has proven remarkably difficult to identify and study such subjects. First, most investigators have been unable to find a credible number of subjects before a nascent or fully expressed immune response has developed. As a consequence, many investigators wishing to document virologic and immunologic events associated with HIV-1 transmission are forced to study "early" or "recently" infected patients after seroconversion, and often lump these subjects together with acute HIV-1 infections in their analyses. We and others have tried to introduce more precision to the definitions of the first stages of HIV-1 infection, and to develop techniques to study subjects and their sexual partners as soon as possible after HIV-1 transmission before seroconversion. Thus, four specific aims are proposed in this study: Aim 1. To establish the CHAVI Acute HIV-1 Infection (AMI) Network comprised of sites in the US, England, South Africa, Malawi, Tanzania, Uganda, Gambia, Botswana, and Zambia, Aim 2. To establish standard operating procedures for identifying patients with acute HIV infection, transmission pairs, and patients that are HIV-1 exposed and uninfected, Aim 3. To establish standard operating procedures for sample acquisition, sample processing, sample transportation, and sample storage, and Aim 4. To transition select Acute HIV-1 Infection (AHI) Network sites from AHI sites to vaccine trial sites over the 7 year CHAVI funding period. Thus, through the establishment of the CHAVI AHI network, Core B will provide the patient samples to CHAVI investigators for a series of critical studies on truly HIV-1 acutely infected patients.